A wide variety of thermoplastic polymers and films formed from thermoplastic polymers are known in the art including, for example, polyethylene terephthalate (PET), polyethylene terephthalate glycol-modified (PETG), and polyvinyl chloride (PVC), and fluoropolymers, among others. Important physical characteristics of such films include their barrier properties, including barriers to gas, aroma, and vapor, such as water vapor, as well as other physical characteristics, such as toughness, wear, and weathering resistances, and light-transmittance. These properties and characteristics are especially important in film applications such as, for example, in the use of films as a packaging material for food or medical products. In many applications, such as medical blister packages, these films are combined with an aluminum foil layer to seal pills therein.
It is known in the art to produce single layer and multilayer fluoropolymer films. Many fluoropolymer materials are known in the art for their excellent moisture and vapor barrier properties, and therefore are desirable components of packaging films, particularly lidding films and blister packages for pharmaceuticals. In addition, fluoropolymers exhibit high thermal stability and excellent toughness. Certain polymers, such as copolymers of chlorotrifluoroethene and vinylidene fluoride have been found to have excellent heat sealability, clarity, and barrier properties when formed into films. However, films formed of these copolymers provide “destructive” seals thereby rendering the seal too strong to separate after being heat sealed. In certain applications, it is desirable to form multilayer “peelable” films that, after being heat sealed, enable the separate layers of the multilayer films to be separated and resealed while maintaining the barrier properties. While attempts have been made to modify the sealing characteristics of films formed of these copolymers (e.g., from “destructive” to “peelable”), polymers of chlorotrifluoroethene are generally incompatible with other polymers, such as olefins, polyesters, nylons, and other fluoropolymers.
Further, in applications including an aluminum foil layer, such as a blister package, access to the pill can be difficult due to the strength of the bond between the polymeric film and the aluminum foil layer, and the strength of the aluminum foil layer to resist pills being pushed therethrough. Even if a user is able to push the pill through the aluminum foil layer, a portion of the aluminum foil layer can break off and may then be ingested by the user.
Accordingly, it is desirable to provide compositions and methods for forming film layers that include copolymers of chlorotrifluoroethene and vinylidene with the films layers sealed to and peelable from each other. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the foregoing technical field and background.